WASHINGTON — Stung by a South Carolina setback that capped a bad week, Mitt Romney said he would release his tax returns Tuesday in hopes of ending a campaign distraction while revived rival Newt Gingrich said he was the strongest Republican to go "toe to toe" with President Barack Obama.

Rick Santorum, third in the South Carolina vote, maintained he was the lone "consistent conservative" left in the race and pledged to keep campaigning in Florida, next on the calendar with its Jan. 31 primary, and beyond.

The newly scrambled presidential contest shifted to Florida after Gingrich stopped Romney's sprint to the nomination with a convincing victory in the first-in-the South primary. For now, that removed the air of inevitability that surrounded Romney's candidacy. But Florida is larger, more diverse and more expensive, and brings new challenges for Gingrich. Once again, he must show he can overcome financial and organizational disadvantages, as he did in South Carolina.

"One of the reasons I think people in South Carolina voted for me was a belief that I could debate Obama head to head, that I could convey conservative values," said Gingrich as the candidates made the rounds of the Sunday talk shows.

"I think we had better be prepared for a tough campaign, whoever we nominate," the former House speaker said. He added, "I can go toe to toe with President Obama on big things. ... I think you can draw a very strong case that in the end the dynamics of a Gingrich/Obama fight are much better for Republicans than the dynamics of a Romney/Obama fight."

Romney said it was "not a good week for me" and cited all the time he had spent talking about his tax returns as his rivals pressed him to make them public before his promised date in April.

After months of resistance, Romney had said last week that he would release tax information for 2011, but not until close to the tax filing deadline. That also was seen as a time, before the South Carolina race rattled his front-runner status, when the GOP nomination might have been decided.

"I think we just made a mistake in holding off as long as we did. It just was a distraction. We want to get back to the real issues of the campaign: leadership, character, a vision for America, how to get jobs again in America and how to rein in the excessive scale of the federal government," said Romney, a former Massachusetts governor and venture capitalist.

Romney disclosed last week that, despite his wealth of hundreds of millions of dollars, he has been paying in the neighborhood of 15 percent, far below the top maximum income tax rate of 35 percent, because his income "comes overwhelmingly from investments made in the past."

"Given all the attention that's been focused on tax returns, given the distraction that I think they became in these last couple of weeks," Romney said Sunday he would release his 2010 returns and estimates for his 2011 returns at the same time "so there's not a second release down the road."

"We'll be putting our returns on the Internet, people can look through them," Romney said. "It will provide, I think, plenty of information for people to understand that the sources of my income are exactly as described in the financial disclosure statements we put out a couple of months ago.

During 2010 and the first nine months of 2011, the Romney family had at least $9.6 million in income, according to a financial disclosure form submitted in August.

Further focusing attention on his wealth was Romney's offhand remark to reporters that his income from paid speeches amounted to "not very much" money. In the August disclosure statement, he reported being paid $373,327.62 for such appearances for the 12 months ending last February. That sum alone would him in the top 1 percent of U.S. taxpayers.

In addition, Romney owns investments worth between $7 million and $32 million in offshore-based holdings, which are often used legitimately by private equity firms to attract foreign investors. Such offshore accounts also can enable wealthy investors to defer paying U.S. taxes on some assets, according to tax experts.

Santorum, who beat Romney and Gingrich in leadoff Iowa, scoffed at the suggestion he might leave the race so conservatives could rally behind Gingrich against Romney.

"The idea that conservatives have to coalesce in order to beat Mitt Romney, well, that's just not true anymore. Conservatives actually can have a choice. We don't have to rush to judgment,' he said.

"The longer this campaign goes on," Santorum said, "the better it is for conservatives, the better it is for our party."

Santorum's continued presence ensures at least some division among Florida's tea party activists and evangelicals, a division that could help Romney help erase questions about his candidacy.

Texas Rep. Ron Paul likely will not be a factor in Florida. He already had said he was bypassing the state in favor of smaller subsequent contests.

As the first Southern primary, South Carolina has been a proving ground for Republican presidential hopefuls in recent years. Since Ronald Reagan in 1980, every Republican contender who won the primary has gone on to capture the party's nomination.

Returns from 95 percent of the state's precincts showed Gingrich with 41 percent of the vote to 27 percent for Romney. Santorum was winning 17 percent, Paul 13 percent.

Already, Romney and a group that supports him were on the air in Florida with a significant television ad campaign, more than $7 million combined to date.

Gingrich appeared on NBC's "Meet the Press," CBS' "Face the Nation" and CNN's "State of the Union." Romney was on "Fox News Sunday," while Santorum was on ABC's "This Week" and CNN.